The present invention relates to buoyancy compensators for scuba divers.
Buoyancy compensators (BCs) are generally made up of an air-tight inflatable vest; a harness system for connection to the diver""s body; an inflation system which can be operated voluntarily (i.e., by the user) via a control and which is supplied with compressed gas, normally air from the breathing cylinder or cylinders by means of a hose which draws air at medium pressure downstream of the pressure regulator of the breathing apparatus; one or more discharge valves which are located in a hydrostatically advantageous position and which can be operated voluntarily by the scuba diver; one or more appropriately calibrated anti-burst automatic-discharge valves; and possibly a member for inflating by mouth on the surface of the water, which may also have the ancillary function of enabling the scuba diver to breathe the air contained within the vest.
It is evident that the primary functions, namely of inflation and discharge, must be performed with fast, easy and safe manoeuvres. It is in this direction that technology has in particular evolved through various generations of inflation and discharge systems.
One first generation of buoyancy compensators for scuba divers was provided with the following: a push-button inflator valve, screwed directly on the vest in a ventral position, and hence easy to grip; a voluntary-discharge and anti-burst integrated valve secured to the vest and positioned on the diver""s shoulder, which could be operated by pulling a short line ending with a special xe2x80x9cpommelxe2x80x9d; and a flexible or corrugated tube, provided with a valve mouthpiece for inflating by mouth and even also for breathing, whenever necessary.
A second generation of buoyancy compensators for scuba divers witnessed the appearance of a new member, referred to as xe2x80x9cintegrated inflatorxe2x80x9d. This is a long corrugated pipe, the top end of which is connected to the vest by means of a voluntary-discharge valve, which can be operated by means of a rudimentary tie rod tucked away inside the corrugated pipe. The bottom end terminates with a gripping part, which, when pulled, operates the aforesaid tie rod, so bringing about discharge. Connected to the latter by means of a press-block coupling is the air-feed hose coming from the pressure regulator of the breathing apparatus. The assembly comprises a push-button inflator valve, which shuts off supply of the compressed air, and when the scuba diver operates the push-button provided, he modulates immission of the compressed air into the BC. A terminal valve, controlled by a second push-button, shuts off access to the vest, so enabling inflation by mouth, or possible breathing, or a further discharge manoeuvre, which proves somewhat complicated and laborious; namely, the user must get hold of the gripping part, lift it above his shoulders, and press the push-button.
The version described abovexe2x80x94which is still by far the one most widely available on the marketxe2x80x94is not without a number of unsolved problems. First of all, an anti-burst automatic valve is required, which involves added costs and encumbrance. In the second place, the problems of hydrodynamic friction are far from being solved, with the risk of the diver getting caught on things as a result of the inflator-pipe assembly which tends to float about in a position that is hard to find (the fact of not being able to find it immediately constitutes a major danger: the functions of inflation and discharge may be of extreme urgency). In the third place, the two push-buttons may be easily confused. In the fourth place, the discharging manoeuvre performed by pulling the corrugated pipe is altogether imprecise: the range of travel of the valve is only three or four millimeters, with the consequent risk of the corrugated pipe getting broken with extremely serious consequences (loss of buoyancy) The discharge manoeuvre performed by raising the hand operating device is, on the other hand, complicated and somewhat contrived, and requires far from ordinary self-control and aquatic skills.
In a third generation of buoyancy compensators for scuba divers, the discharge valve is remotely controlled by the hand operating device of the inflator, by means of a pneumatically controlled valve. When the scuba diver wants to discharge, he presses the push-button provided and, by means of a tube hidden inside the corrugated pipe of the inflator, he sends a pneumatic signal to the discharge valve located on his shoulder, the said discharge valve being pneumatically controlled. The advantage of this solution lies in the fact that the imprecise manoeuvre of xe2x80x9cpulling the corrugated pipexe2x80x9d of the second generation is not required. One disadvantage is the greater complexity of the pneumatic servo-valve system, the risk of air leakages, and the need for maintenance and periodic replacement of the gaskets.
A fourth recent generation of BCs is described in the documents EP-A-921064 and EP-A-945339. The inflator with its traditional corrugated pipe disappears, whereas there appears an integrated control block, which is connected to the vest in a ventral position and which can be gripped by the user with his left hand, the air-feed hose being connected to said control block and two push-buttons being provided therein. The first push-button makes it possible to inflate the vest by opening the valve that shuts off the medium-pressure air coming from the air-feed hose. The second push-button, which is for discharge, sends a pneumatic signal by means of a system of pressurized tubes tucked away inside the vest to two or more pneumatically controlled discharge valves which open simultaneously. The evident advantages are that there no longer exists the effect of encumbrance, with the danger of the diver getting caught on things and having his movements hampered and slowed down by the corrugated pipe+air-feed hose ensemble floating about in an position that is anything but easy to define. Furthermore, the diver no longer has to move his hand to carry out the inflating/discharging sequences. Less evident, but serious, are the disadvantages: 1) The pneumatic control for discharge is somewhat primitive and imprecise. It cannot be modulated and is liable to burst open suddenly all the valves connected to it. The only way for discharging in a more or less modulated manner is a series of open-close-open-close manoeuvres. This procedure is difficult, and in a situation of emergency and mental confusion, dangerous. 2) The device consumes compressed air which is precious for breathing, increasing air consumption during diving, with consequent drain on autonomy. 3) At the end of diving, when the pressure in the cylinders is very low, the device might not operate on account of shortage of pressure; and yet, this is precisely the most delicate moment, when the scuba diver, who is light because the cylinders have almost run out (4 to 5 kg is the difference in weight between the cylinders at start of diving and end of diving), tends to float, being moreover in the process of surfacing. The increase in the specific volume of the air contained in the vest tends to cause xe2x80x9cballooningxe2x80x9d, which is very dangerous on account of the risk for the diver of phenomena of aeroembolism. At the very moment when the need for discharging air is impellent, the pneumatic servo control might get stuck on account of low pressure, with possible tragic consequences. 4) The constructional complexity of the mechanical-pneumatic ensemble is considerable. The device requires periodic maintenance, as well as checking and replacement of the numerous gaskets and flexible tubes, with an added complication if they are buried away somewhere inside the vest, and hence difficult to inspect.
A fifth generation is disclosed i U.S. Pat. No. 5,256,094, also providing a remote integrated control assembly, arranged in a ventral area of the vest which is easily accessible by the diver""s hand, but not fixedly secured to the vest. This control assembly includes a first push-button or trigger to operate opening/closing of the discharge valve and a second push-buttom to activate the inflating system. The first push-button activates a remote control consisting of a cable connected to the discharge valve which in turn is applied to the rear area of one vest shoulder. The cable is housed within a simple tube, by pulling on any portion of which the discharge valve can be activated. As to the inflating system, this known control assembly is connected to the air supply hose and thus, through the second push button, to the vest via a long inflating flexible tube going up from the ventral area to the shoulder of the vest at which the inflating valve is also provided.
Also this known arrangement is affected by several drawbacks.
Firstly, the arrangement of the cable within the related freely extending tube makes opening operation of the discharge valve inaccurate and not al all safe: in fact, when the cable is subjected to traction following actuation of the first push-button of the control assembly, the disharge valve is also being pulled in its entirety, i.e. drawn towards the control assembly, owing to the limp and flexible nature of the vest tissue on which the valve is secured. Such a displacement of the discharge valve as a whole evidently leads to an unsteady opening performance of the valve, or even to uncomplete or failed opening thereof. On the other hand, the discharge valve is subject to the risk of undesired opening in case the tube along with the cable is housed be pulled from the outside, for instance following accidental hooking thereof by an underwater obstacle.
Secondly, the fact that the control assembly is not fixedly secured to the vest is a limit to access ease and convenience for the user. Thirdly, the inlet path of the inflating air through the long tube provided downstream of the control assembly involves huge losses of pressure downstream of the air expansion site, i.e. after the air has already expanded at a great specific volume. This rusults in practice into a very slow vest inflating, which is inadequate during regular buoyancy compensations and quite dangerous in emergency situations.
As regards the conformation of the inflatable vest, currently known buoyancy compensators for scuba divers can be basically divided into two types: xe2x80x9cdouble-bagxe2x80x9d ones and xe2x80x9csingle-bagxe2x80x9d ones.
In general, and in the present context, by xe2x80x9cdouble-bagxe2x80x9d BC is meant a buoyancy compensator in which the bag is made up of an external bag and an internal bag, which are different and independent from each other. The internal bag in practice consists of a hermetic and inflatable inner tube, while the external bag consists of a resistant coating made of non-inflatable, inextensible woven fabric, which is permeable to air and to water, possibly also thanks to appropriate meshwork inserts or holes with eyelets.
In the case of xe2x80x9csingle-bagxe2x80x9d BCs, the vest actually consists of a single bag, which is, at one and the same time, resistant and hermetic (in so far as it is made by welding peripherally at high frequency two layers or sheets of woven fabric spread with polyurethane), inflatable, inextensible, and resistant to pressure, abrasion, tearing and perforation.
The two traditional configurations described above are illustrated, by way of example, in FIGS. 12 and 13, which are schematic cross-sectional representations respectively of the single-bag structure, deflated in the case of FIG. 12A and inflated in the case of FIG. 12B, and of the double-bag structure, deflated in the case of FIG. 13A and inflated in the case of FIG. 13B.
At present, the constructional trend is generally in the direction of the single-bag structure, basically for economic reasons, reasons of an aesthetic nature (i.e., styling), and on account of the possibility of partial automation of the manufacturing process. The tendency is to use the double-bag configuration only when the aim is to achieve less customary results, such as larger inflation volumes, or else a greater softness of the parts that come into contact with the user""s body. Recently, the single-bag structure has revealed its serious limits when manufacturers attempted to extend the inflatable area, beyond the ventral region, to include also the rear areas on either side of the compressed-air cylinder. In these cases, in order to achieve three-dimensional volumes, manufacturers were forced to adopt complex and costly structures on account of the welding requirements, the said structures moreover being far from effective owing to the small volume even so achieved and the poor xe2x80x9cconnectionxe2x80x9d to the diver""s body of the floating items, which in practice drift about here and there in the water (see EP-A-0 974 514).
The primary object of the present invention is to provide, as far as the inflating and discharge functions are concerned, an innovative generation of buoyancy compensators for scuba divers, designed to achieve the advantages (where these exist) of the previous generations, while overcoming their drawbacks as referred above.
The above object is achieved mainly thanks to a buoyancy compensator for scuba divers as defined in appended claim 1. The pre-characterising portion of claim 1 reflects the prior art known from U.S. Pat. No. 5,256,094.
In summary, the buoyancy compensator according to the invention is provided with a device named xe2x80x9csingle controlxe2x80x9d which is operable both to inflate and to deflate the vest, wherein the single control is permanently secured to the vest at a fixed site which is easily accessible in a prompt way by one user""s hand, and is also providing a direct and immediate inlet of the air through the securing site itself of the single control, i.e. via an extremely short low-pressure duct, and with a discharge function operating lever or trigger which actuates an inextensible cable slidable along a flexible but resistant-to-compression sheath which is backed at both opposite ends thereof, so that discharge sensitivity be constant and influenced neither by variations of the air volume within the vest, nor by the diver""s movements in use, nor by crimping of the vest.
The so conceived single control assembly mainly performs two functions:
A. inflating of the inflatable vest, by means of a push-button operated valve and the like, fed with air through a quick-fit connector and a hose, from the main pressure section of the regulator. Inflating can be adjusted and modulated intervening both on the instantaneous flow rate (depressing more or less the push button) and on the actuating time. Air inlet into the vest is immediate: the path between the valve and inflatable chamber of the vest is only a few millimeters long and thus does not generate any relevant loss of pressure, whereby inflating is most prompt.
B. rapid and adjustable discharging of the air contained in the inflatable vest. The push button or trigger or lever mechanism pivoted on the single control body applies a direct traction onto the inextensible cable (preferably made of stainless steel or inextensible synthetic material). The cable, within the backed sheath, goes up from the ventral position to the shoulder entering the discharge valve therein, which operates a disk obturator by means of a rocker lever. The cable must necessarily be made of an inextensible material, i.e. it must not be subjected to any lenght changes either under traction stress or following umidity variations.
One peculiar aspect of the system according to the invention resides in the sheath backed at both ends. In one exemplary embodiment of the invention, the sheath is including several component elements fitted onto a helically wound spring coil made of stainless steel.
Differently from all the above-mentioned known solutions, namely that according to U.S. Pat. No. 5,256,094, the sheath is compulsorily provided to be both resistant to and unaffected by compression, i.e. it does not become shorter when subjected to compression. Actually, when the cable applies a traction strain (it is a stay wire), the sheath must react as a prop: in other words, it must avoid that when the diver operates the discharge push button or trigger provided on the single control, the discharge valve may move closer thereto owing to crimping of the vest.
Air discharge can be modulated in connection with the intantaneous flow rate of the discharged air, with the time length of the discharge action, and also with the total volume of the discharged air as a result of both the flow rate and time. It can thus be argued that both a xe2x80x9cquick dischargexe2x80x9d function (necessary to enable relevant and sudden variations of the buoyancy attitude) and a xe2x80x9cfine dischargexe2x80x9d function (i.e. a millimetrical buoyancy trimming adjustement) can be achieved by means of successive operating pulses onto the discharge trigger which are short in connection with both their operating stroke and time.
Another difference with respect to all the known mechanical solutions, which not having a backed sheath can perform air discharge in an unsafe and unreliable manner (namely only when the vest is by chance crimped only less than a certain amount), the solution according to the present invention is capable both to discharge large amounts of air (quick deflating) and to finely modulate the discharge amount (adjustement). Such, a modulation well distinguishes the invention over the known solutions according to the fourth generation disclosed in the above, which as already stated do not provide a fine discharge option since the pneumatic actuator of the discharge valve(s) can only be set on or off: such an arrangement in fact consists of a piston which xe2x80x9cfiresxe2x80x9d the actuator either to the open or to the closed position, without any chances to modulate the stroke thereof. Its only modulating capability is bound to the manual actuating time, which is however really hard to perform in critically difficult underwater situations.
As compared to the buoyancy compensators according to the fifth generation (U.S. Pat. No. 5,256,094), the B.C. according to the invention also achieves a series of relevant advantages: by virtue of the cable sheath backed at both ends, the discharge valve as a whole is not shifted by the traction applied to the cable, whereby opening thereof is carried out in a safe and precise manner. Any risks of undesired opening owing to an accidental traction applied to the sheath, whose opposite ends are fixed, is also prevented: this advantage can even be further enhanced placing the sheath and cable assembly within a hidden and protected area of the vest. Moreover, fixedly securing the single control to the vest enables it to be easily found in use, and the direct connection between the air supply hose and the vest drammatically reduces any pressure losses thus ensuring inflating promptness.
The various functions and manoeuvres are intuitive to the user: without needing to look, the scuba diver brings his left hand onto his ventral region, locates the single control, grips it opposing his thumb to his other fingers. If he presses the inflating button with his thumb, the vest inflates; if he presses the finger control of the discharge lever with his forefinger and middle finger, the vest deflates, the two operations being performed in a simple, intuitive, ergonomic and fast way, with the amount of inflation or deflation which can be precisely modulated.
Additional advantages afforded by the buoyancy compensator for scuba divers according to the present invention may be summed up as follows:
1) It does not use the concept of xe2x80x9cpneumatic interlocking of the discharge valvexe2x80x9d described in reference to the third-generation and fourth-generation BCs. Consequently, it does not consume precious air, it operates also when the cylinder has run out, and, as compared to the fourth-generation BCs, it is not abrupt or rudimentary in its modulation.
2) The single control of the BC according to the present invention is easy for the scuba diver to locate with his hand and is connected directly to the BC, in a ventral position, and it is readily identifiable unlike the controls in the third- and fifth generation BCs.
3) As compared to all the corrugated inflators (both those of second-generation and those of third-generation BCs), it does not present any hydrodynamic friction, any danger of getting caught up in things, or any increase in overall dimensions.
Furthermore:
a) It enables concentration of the two primary functions of inflation and deflation in a fixed and accessible position, with an ergonomical advantage;
b) It enables graduated discharge with fine modulation by pressing on the lever for a greater or lesser number of millimeters (geometrical adjustment) and/or for a greater or lesser number of seconds (time adjustment).
c) It enables use, for discharge, of an ordinary discharge valve of the overpressure type for BCs, which, in addition to the manual-operation function, opens automatically when the pressure inside the vest exceeds the calibration value (anti-burst function).
d) It enables calibration of the discharge function by acting on the cable/sheath length, using simple mechanical means.
e) It does not requirexe2x80x94as regards the discharge functionxe2x80x94any pneumatic maintenance, such as periodic replacement of the gaskets, and does not present any risk of leakages.
It should be pointed out that the elements for controlling inflation and deflation could, instead of being grouped together in a single integrated assembly (single control), consist of physically separate members applied in areas of the BC that are just contiguous, or even separate. In any case, the function for control of discharge will come under a mechanical remote control made up of a flexible tie rod operated by a manoeuvring lever, more conveniently in the form of an automatically grippable hand operating device, which is immediately accessible by the user""s hand and which can be actuated in a graduated and modulated way by opposition of the user""s thumb to his other fingers.
Further secondary characteristics are defined in the subclaims 2-13.
Another particular object of the invention, with specific reference to the structure of the inflatable vest of the buoyancy compensator, is to overcome the drawbacks of the known arrangements disclodsed in the above, while achieving the peculiar advantages of the first and of the second known solutions.
According to the invention, this object is achieved by means of a buoyancy compensator for scuba divers.
In brief summary, the buoyancy compensator for scuba divers according to the invention presents a xe2x80x9cmixed structurexe2x80x9d, i.e., a single-bag structure in the areas where this technological solution proves useful and advantageous because the said areas are subject to mechanical loads (on account of the presence of the harness, the attachments for valves and for the bottle(s), etc.), and a double-bag structure in the other areas, namely where there is a higher requirement of inflation to enable expansion without constricting the diver""s chest during use.
According to a further otional feature of the invention, the buoyancy compensator of the invention may be provided with a self-supported ballast system which, instead of being fitted within receptacles arranged in the front area of the inflatable vest, as in the prior art, is housed in pockets or containers carried by wings of fabric or the like so as to surround the air bottle(s), and secured thereto by means of belts or straps, in a fixed fashion.
Three main advantages in use are thus achieved with respect top the traditional arrangements providing front xe2x80x9cdanglingxe2x80x9d ballast receptacles:
1. the ballast does not compress any more the diver""s chest or abdomen, particularly in the inflated condition of the vest;
2. the ballast mass is no more free to oscillate and hit the diver""s body (when walking out of the water, when plunging, when climbing a boat ladder);
3. the center of gravity of the ballast is coinciding with the air bottle(s) volume (which, according to the Archimedes"" principle is the center of gravity of the floating attitude of the bottle while it is being progressively discharged: as it is known, the weight of a 15 liter bottle under 200 bar, thus containing 3000 liters of compressed air, is reduced after discharge of 4 Kgs.), thus preventing upsetting couples.